Magnetic disc storage devices known as disc drives are used in conjunction with digital computers to store both data and programs. A single disc, or a stack of discs known as a disc pack, may be used. The discs of the disc pack are divided into a number of addressable cylinders of as many tracks each as there are disc surfaces in the pack, one track on the upper surface of each disc and the other on the lower surface. Either a single movable magnetic head, or a number of fixed magnetic heads, are magnetically coupled to each of the two surfaces of each disc in the disc pack to perform the reading and writing functions. The test unit of the present invention finds particular utility with disc drives of the movable head type.
There are a large number of different disc drives on the market today. Test units for each of the different types of disc drives are available. However, the objective of the present invention is to provide a portable programmable disc drive qualifier, which has universal application and which, as mentioned above, can be used to exercise and/or qualify most if not all of the better known disc drives on the market today. Specifically, the various disc drives which are presently available include 25-80 megabyte storage module drives, such as the Certainty 270 Series of Control Data Corporation, or the Ampex DM-900 Series.
The disc drive qualifier of the present invention is intended for verifying correct drive/media performance in a user environment to assure reliable data handling. It is also intended as a diagnostic tool for use in field service, and in the engineering laboratory during disc drive development. The unit may also be used for exercising disc drives under burn-in or other conditions. The low cost, high speed and extreme versatility of the disc drive qualifier of the invention makes it attractive for the foregoing and other applications. In addition, a software configured interface makes the qualifier of the invention applicable for testing other disc drives at a small software development cost.
The disc drive qualifier of the present invention is particularly adapted for use in conjunction with the storage module type of disc drive, such as those identified above. However, by software changes and cable adapters, the qualifier can be used in conjunction with other disc drives, for example, disc cartridge drives, such as the Microdata Marathon Models 7401, 7402; disc pack drives, such as the Ampex DM-9000 Series; and fixed disc drives such as the Memorex Models 550, 552, Shugart Model SA-1000, Lobo 7000 Series, and IMI 770 Series.
With the advent of the programmable disc drive qualifier of the present invention, an extremely powerful piece of test equipment is now available to the disc drive user. The qualifier makes possible the testing of disc drives and disc packs by non-technical personnel. The unit also provides the abilities to format disc packs, to flag and readdress faulty sectors, and to reduce by an order of magnitude, the time required to perform a head alignment, without the endless adjusting and lengthy error calculations normally associated with that task. Many of the other test features included in the qualifier also make it extremely useful to the trained field engineer. In fact, the qualifier of the invention is more useful than the prior art units tailored to particular disc drives. The qualifier of the invention, unlike the prior art units, can be programmed to work with all SMD (Storage Module Drive) format units and most non-SMD formats.
An important feature of the qualifier of the invention is the lack of the array of binary switches normally present in the prior art units, which are used to code entries for head number, cylinder number, address, and data information. These have been replaced with two key pads in the embodiment to be described; one for functions, the other for numeric quantities. A moderately simple test, which would be beyond the scope of the typical exerciser, can be entered easily on the qualifier. An example of this would be as follows:
[SEEK CYL] [152] PA1 [SELECT HD] [3] PA1 [LOAD DATA] [RANDOM] PA1 [WRITE] PA1 [READ]
This program would seek cylinder 152, select head number 3, generate a random data word, place the data in the write data register, write the random data in all sectors and read the data in all sectors. The operator would see, in the display windows, the write and read registers represented by two rows of LED's. The first would reflect the data in the write data register while the second would show the read back data. The operator could then depress the Error Count key and the alphanumeric display would indicate ERROR COUNT. By using the INCREMENT CYLINDER, INCREMENT HEAD, and REPEAT keys, programs can be written to check out the disc pack in its entirety, or any portion thereof. Additionally, the program can be constructed such that the test will halt at each error or will continue to the end, maintaining a cumulative error count.
Another important feature of the qualifier of the invention is the ability to call up pre-programmed diagnostic routines from PROM. An all-cylinder, all-head test with certain test algorithms may be placed in PROM to be called by entering [DIAG] [3], for example. The diagnostic routine would then run automatically and cumulative error and pass counts would be stored. This would allow a relatively low level operator to carry out extremely sophisticated test programs without being required to either understand the test or to make judgments about the test results. Should there be reason to doubt the test results, diagnostic programs for the self-test of the qualifier are also provided. By making proper use of the diagnostic programs, a user may monitor his drive units on a regular basis to determine when operating margins are being approached. The required service and adjustment may then be called for before any failures, and their resultant down-time, occurred.
One of the most tedious tasks for which a disc drive exerciser is used is to perform head alignment. The requirement for head alignment is common to all drives, and the task is made more difficult by the nature of the exercisers themselves. In SMD drives, one surface contains the servo tracks, which the servo head follows. The remaining heads are mechanically aligned to the servo head such that they are in equivalent positions on the other surfaces. To perform this alignment, in all drives, a C.E. disc pack is inserted in the drive. The C.E. pack simply makes all surfaces servo surfaces.
Each manufacturer's drive interfaces with the disc drive head alignment circuits in a different way, so usually an exerciser with head alignment capability can interface to only one type of drive. The qualifier of the invention, however, has the servo electronics in the unit itself, and is provided with cables to permit interfacing with many different types of disc drives. The available prior art units include a zero-center null meter, calibrated in micro-inches, and a reversing switch.
In the qualifier of the present invention, the reversal switching is accomplished automatically at high speed and the null signal is read by an analog-digital (A-D) converter. The A-D converter, through software, drives the read data register LED's such that all but two are lit. The dark pair indicates position off null. The operator adjusts the head so that the dark pair is in the center of the display, and reads the total, effective misalignment directly in micro-inches from the alphanumeric display. The need for calculations and judgments as to magnitude equalities is eliminated.
The qualifier of the invention also provides LED indicators for status signals from the drive, including READY, SEEK END, ON CYL, SEEK ERROR, FAULT and HIGH TEMP. Thirty test points are also available. These permit synchronization from and observation of such signals as SERVO CLOCK, SECTOR MARK, INDEX MARK, ADDRESS MARK FOUND, DATA ERROR, READ CLK, etc., as well as BUS BITS 0-10.
A random access memory (RAM) provides storage for keyboard entered programs as well as the error count and pass count registers. Because the microprocessor cannot operate in real time at normal disc data rates, a second RAM is provided. During a normal write to disc operation, for example, the microprocessor loads a sector of data into the second RAM. This data is then transferred to the disc drive in real time. When a disc pack is being formatted, the data in the second RAM remains fixed except for incrementing the address for each sector. So that no time will be lost between sectors for the microprocessor to reload this redundant data, a portion of the second RAM is accessible by the microprocessor while a write is in progress. This permits the microprocessor to increment the address while the disc is being written with the data field. In terms of formatting time, this means a complete track can be formatted for each revolution of the disc.
A fully implemented RS-232-C serial port with selectible baud rate allows simple connection of printers, cathode-ray tubes, modems or terminals. Error detection may be achieved by comparison of read data with write data, or by evaluation of an error correction code. As mentioned above, all errors, or only uncorrectible errors, can be detected and logged, as described. Disc packs written with another controller may be analyzed for error content based on evaluation with the error correcting code field. Sectors may be located by sector mark or by address mark. The entire sector may be written, or the data field and error correcting code may be written exclusively.
The qualifier of the invention has a prompting mode which provides instruction messages to the unskilled operator, and leads the unskilled operator step-by-step through procedures, such as operating the unit, testing, qualifying or formatting a disc drive, or pack, or repairing a faulty drive. The messages may, for example, direct the operator to make certain tests and, based on the results, suggest a corrective action, such as replacing a circuit board, and then directing certain other tests to realize a solution to a particular problem by following a trouble-shooting schedule. Self-test diagnostics are also included in the test unit of the invention to verify that the unit is operating correctly.
In summary, the disc drive qualifier unit of the present invention is a complete software supervised microprocessor controlled disc controller intended for test and diagnostic purposes. High speed is achieved because actual testing is done by hardware circuits in real time at disc speed. Extreme flexibility and simple programmability to perform countless variations of special test sequences is achieved by software supervision of hardware circuits. Computer control formatting and head alignment simplifies and shortens these operations.
Briefly stated, the disc drive qualifier of the present invention is an extremely versatile microprocessor controlled unit for diagnostic testing and exercising of a variety of types of storage module disc drives, and which can be easily modified for testing and exercising other disc drives.